This invention relates generally to liquid level control devices and, in particular, to a fluidic level control system which may be utilized to control the flow of liquid into a reservoir, storage tank or other container and to control the level of liquid therein. The device of the present invention is particularly useful in an application where automatic shut-off features are desirable.
For instance, in U.S. Pat. No. 3,703,907, a fluid amplifier is disclosed having an inlet and an outlet zone and adapted for use in a liquid reservoir to sense a change of liquid level therein. The amplifier is adapted to be positioned adjacent the desired liquid sensing level in the reservoir and for directing a power stream substantially transversely to the surface of the liquid in the reservoir. Inlet means is constructed and arranged such that a fluid power jet is abruptly altered when the liquid level in the reservoir rises to a sensing level. This abrupt alteration develops a fluid pressure signal which may be used to control various apparatus, such as a pressure responsive fluid valve.
Such fluid amplifiers have been used in various applications. My copending patent application Ser. No. 491,521, filed May 4, 1983 discloses the use of fluid amplifiers in a filling device for use in connection with maintaining proper levels of electrolyte in individual cells of industrial batteries. My copending patent application Ser. No. 404,070, filed Aug. 2, 1982 shows the use of a fluid amplifier wherein the sensing level of liquid in a reservoir is at a remote point from the fluid amplifier itself. My copending patent application Serial No. 614,550 filed May 29, 1984 discloses a novel fluid amplifier using a "dual-jet" system. One jet is a major supply stream, and the other jet is a smaller fluid power stream which flows substantially parallel to the major supply stream. A signal developing device is provided for receiving a fluid pressure signal of one magnitude when the smaller power stream is generally parallel to the main supply stream and of a second magnitude when the smaller power stream is altered.
Fluid amplifiers of the character described also have been used in automatic shut-off nozzles as disclosed in U.S. Pat. No. Re. 29,715 wherein a nozzles is shown particularly useful in an application such as self-service gasoline retail outlets.
Most of the fluid amplifiers described above have been used in types of applications where liquid level control systems require a flow of liquid to provide operating power. In some applications this liquid is supplied from a recirculation system, such as a swimming pool filter pump. In other cases, the fluid amplifier is supplied with liquid when a refill valve is opened manually or by a separate control. The fluid amplifier then is used to shut the refill valve off at some predetermined level. This type of control is called high level cut-off with manual rest.
Some applications require a level control system that has automatic reset when the level falls below the shut-off point. For these types of applications, mechanical floats or electronic probes are generally used to turn the system on. However, with the development of a self-diverting amplifier as shown in my application Ser. No. 491,521 and a "dual-jet" amplifier as shown in my application Ser. No. 614,550, it has been found possible to use a fluid amplifier to turn a system on from a complete power-off condition. This is possible because these amplifiers can store potential energy, in the form of a hydrostatic pressure signal when they shut off. When the liquid level drops below the amplifier outlet and this pressure signal is released, it can be used to actuate a pressure switch or diaphragm control valve. The present invention is directed to providing such a novel system.
In other words, a drawback of prior systems utilizing fluidic principles described above is that the systems must operate with "on power". The present invention can operate from a power-off condition.